I have not done this but just over the bridge on Perdidio Key there is a beach access you might be able to put the boat on the sand there. You would be just outside the bridge. Watch out for the rocks if you go out the pass you'll want to stay close to the channel. Also the swells can be heavy in the pass.

I know there is a boat ramp on Ono Island, but it is private. There are also several marinas around but they are located in more protected waters.

Good Luck and let us know where you end up launching.

Kent